Re: [PATCH V5 13/21] riscv: compat: process: Add UXL_32 support in start_thread
From: Palmer Dabbelt <palmer@dabbelt.com>
Date: 2022-02-23 01:43:02
Also in:
linux-arch, linux-arm-kernel, linux-mips, linux-riscv, linux-s390, lkml, sparclinux
On Tue, 01 Feb 2022 07:05:37 PST (-0800), guoren@kernel.org wrote:
quoted hunk ↗ jump to hunk
From: Guo Ren <redacted> If the current task is in COMPAT mode, set SR_UXL_32 in status for returning userspace. We need CONFIG _COMPAT to prevent compiling errors with rv32 defconfig. Signed-off-by: Guo Ren <redacted> Signed-off-by: Guo Ren <guoren@kernel.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Palmer Dabbelt <palmer@dabbelt.com> --- arch/riscv/kernel/process.c | 5 +++++ 1 file changed, 5 insertions(+)diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c index 03ac3aa611f5..1a666ad299b4 100644 --- a/arch/riscv/kernel/process.c +++ b/arch/riscv/kernel/process.c@@ -97,6 +97,11 @@ void start_thread(struct pt_regs *regs, unsigned long pc, } regs->epc = pc; regs->sp = sp; + +#ifdef CONFIG_COMPAT + if (is_compat_task()) + regs->status |= SR_UXL_32;
Not sure if I'm just misunderstanding the bit ops here, but aren't we trying to set the UXL field to 1 (for UXL=32)? That should be a bit field set op, not just an OR.
+#endif } void flush_thread(void)
Additionally: this isn't really an issue so much with this patch, but it does bring up that we're relying on someone else to have set UXL=64 on CONFIG_COMPAT=n systems. I don't see that in any spec anywhere, so we should really be setting UXL in Linux for all systems (ie, not just those with COMPAT=y).